The present invention relates generally to an image signal reproduction device for a solid-state image sensor and, more particularly, to a reproduction circuit device for reproducing an output image signal picked up by a solid-state image sensor, which image sensor is swing-driven to periodically shift in position relative to the incident image light.
A swing-driven imaging technique for producing an image of high resolution, the degree exceeding the actual number of picture elements or pixels, by employing a solid-state image sensor having a limited number of pixels is known among persons skilled in the art. According to this specific imaging technique, a solid-state image sensor is typically arranged so as to vibrate or swing in a plane orthogonal to the incident image light, horizontally, perpendicularly, and relative to the image light in a given vibration mode. When the sensor is applied to an NTSC television system in which one frame consists of two fields, the image sensor swings so that it senses the incident image light at different sampling positions during the different field periods. As a result, the reproduced image picture has doubled resolution, which corresponds to the resolution obtained by a fixed image sensor having twice the number of pixels.
The image signal obtained by such a swing-driven image sensor includes a reset noise component (e.g., approx. 500 mV) and a DC offset component (e.g., approx. 5 to 10 V). Therefore, it is necessary to reproduce an image of high enough quality that the noise components can be removed from the CCD output signal without causing waveform deterioration of the rectangular image signal components. It is desirable that a linear detection circuit be used for removing the noise components.
The commercial production of the linear detection circuit arrangement, however, is difficult since the cicuit is required to have very high frequency characteristics. In order to carry out the image signal processing without deteriorating the image signal component in a case where the frequency fcp of a clock pulse of the image sensor is 7.16 MHz, it is necessary for the linear circuit to pass tertiary high frequency components contained in the image signal and, consequently, the frequency band of the linear detection circuit must be at least 20 MHz or more. In a detection circuit having a wide frequency band, deterioration of the signal phase characteristic cannot be avoided. As a result, a problem arises in that amplitude distortion is generated between the image signals occurring in both fields and this causes flicker noise.